The objective of the study is to observe the effect of adherence to once-daily administered long-acting bronchodilators (long-acting ß2-agonists [LABAs] / long-acting muscarinic antagonists [LAMAs]) on patients health related quality of life (HR-QoL) and to assess the relation between symptoms improvement and adherence to Chronic Obstructive Pulmonary Disease (COPD) maintenance therapy